RPi 4 very slow to non existent ETH

My Pi 4 runs great, works well and has no real issues.
Networking is setup to be a WiFi hotspot so that I can connect tot he pi and works really well and is fast.

Ethernet on the other hand is a hot mess.

Ive used this disk image on other Pis and not really noticed any issues previously, however I am testing a lot more on this Pi4 with Ethernet, so maybe that is why I am noticing it now.

The Issue:
I plug the Pi4 into my managed switch and it gets connectivity and all is visible, however, it is really, really, really slow.
Ive been living with this the past month or so and it’s been a pain, but sorta works.

Today I plug it in and I have zero connectivity.
Managed switch and the Pi4 end both have connectivity and activity lights.
Router cant see it.
WiFi works fine.

I need to have ETH connectivity however as I need access on my local network for both connecting to the Pi4 and giving it internet access.
Ive tried different cat5 cables and different ports on the switch as well as rebooting, to no avail.

Lastly, I’ve plugged the same cat5 cable into my laptop and it all works perfectly.

Does this issue sound familiar to anyone and does anyone have ideas as to where to begin to look?

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Hi Andrew,

I’m not the networking guru but might be able to get you started at least :slight_smile:
Other Makers report that doing the following may help:

  • Removing as many USB and GPIO peripherals as possible
  • Ensuring that the switch/router has identified that ethernet interface as a full gigabit connection
  • Try flashing a new Pi OS instance onto a microSD card and testing from a fresh install

This topic touches on a few possible improvements with a successful outcome:

Are you able to paste in any speed test outputs? If they clamp at a distinct speed we might be able to determine whats causing issues there!


Thanks Liam,
I’ll give the suggestions a go, however I did manage to do a

sudo apt-get upgrade

and the connection seems a little more stable now.
Interesting point though, Im not able to run a

sudo apt-get update

as it throws a:

W: GPG error: http://www.deb-multimedia.org jessie InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 5C808C2B65558117


Ethernet seems to be moderately OK now after the ugrade, but I’ll run some speed tests regardless.


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Replying to myself :slight_smile:
In playing around with cables testing another issue I inadvertently powered down the pi and had to reboot.

While I still have connectivity, it is on a go slow again now. sigh.
Going to need to look further into the error I think, or I’ll just re-image it and see if that fixes the issue.

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See if this helps Andrew for the GPG key issue.

You should replace the ‘miising public key’ string with 5C808C2B65558117

Hopefully it will resolve the gpg issue.

For the slow ethernet, check if the soldering of the port on the board is all good. A good magnifier will help or a smart phone with a good zoom function will also work.


thanks, Ill give it a go